Method of joining carbon bodies



j ggs; 1051.22, 1 v I UNITED STATES PA TEN oFF cE METHOD or 101mm; CARBON Booms v Charles DesmondGreaves and William Derrick Cor-lass Walker, London, England, 'assignors to r ish company C.-,D. Patents Limited, London, England,a Brit- Application September 16, 1947, Serial No. 774,411

In Great Britain July l2, 1946 Section 1, Public Law 690, August 8,1946 Patent expires my lg, 1966 5 Claims. (or. 154-116) the junction of any material otherthan'ca'rbon.

Yet carbon junctions presenta difilcult problem. This element is highly refractory, is not amenable to welding technique, and is moreover oxidized in air at even moderate temperatures. Hitherto it has been usual to incorporate noncarbon parts into the junctions betweensuch carbon units, with corresponding loss of eiliciency. v

This invention consists of a method of joining separate carbon parts with a carbon bond, by placing together the surfaces which are to be joined and passing an electrical current through hydrocarbons; distillates from coal tar; crude coal tar, with or without washing; coal tar residues such as pitch; petroleum distillates or residues, preferably those of high carbon content such as asphaltic or pitch-like residues; haturally occurring asphalts which are liqueflable without decomposition; and heterocyclic bodies, such as pyridine,.and substituted bodies such-as aniline, which melt without decomposition.

Suitable carbonaceous fluids are for example ethylene, benzene, toluene or dicyclo-pentadiene. Unsaturated hydrocarbons or aromatic hydrocarbons are especially suitable carbonaceous fluids, but saturated hydrocarbons may also be used although they may require the use of somewhat higher temperatures.

The nature of this invention-and the manner in which it is performed will be appreciated from the following description of an example, reference being made to the accompanying drawing in which:

Figure 1 is a diagram in front elevation, and

, 2 v Figure 2 is a diagram in side elevation of a laboratory apparatus for carrying out the method of this invention.

Two carbon tubes I2 of internal diameter, external diameter and2" ,longfhaving end faces normal to their axeswere placed each in an electrically insulated clamp 13 carried on a stand I4 which supported the tube in a horizontal position at a' height of about 2'j above the, bench l5. The end faces to be joined were brought together within the annular conduit it having four radially disposed and equally spaced nozzles l1 projecting inward from the conduit IE to a distance of about from the junction between the end faces ofthe carbon tubes l2. The base of the conduit |6fwas supported on, the

bench l5, through which "a pipe connection l8- wasmade to the interior of theconduit I'B from a cylinder of ethylene gas (not shown). Two electrical leads I9, each with a brass clip 20 attached,,were taken through'the bench l5 to the output side of a transformer (not shown), which gave a current of 200 amps. at 6 volts with the resistance used. a The brass clips 20 on the leads l9 were secured one to the extreme end of each carbon tube l2. Near the junction of the end faces a pipe connection 2| was made through the bench to a cylinder of nitrogen (not shown),

and the whole area on the bench thus utilized was covered by a bell-jar 22.

The regulator on the nitrogen cylinder was then opened, the volume flow being suflicient to maintain a positive pressure within the bell-jar 22. The electrical current was switched on. When the area at the junction between the end faces of the tubes was heated to bright red heat (about 800 C.), the regulator on the ethylene gas cylinder was opened so that the supply of gas from the nozzles 11 was at a. pressure of 3 to 4 lbs. per square inch. above that prevailing inside the jar. The ethylene jets thus directed at the junction decomposed rapidly leaving a bright carbon deposit of graphitic appearance. As the carbon was deposited the resistance at the interface decreased, and the process was concluded when the temperature of the tubes, as judged by the colour, had become uniform along their entire length. When withdrawn after cooling the tubes l2 were united together.

We claim:

1. A method of bonding together separate carbon parts with a bond of carbon which method consists in placing in contact the surfaces to be bonded, surrounding the said surfaces with an atmosphere which does not decompose to liberate carbon and which does not react with.

carbon at bright red heat, raising the temperature of the carbon surfaces to be bonded to bright red heat by passage of an electric current between the said surfaces and directing at the junction of the carbon parts a stream of carbonaceous fluid which is decomposable at bright red heat to deposit carbon in a hard strong condition and which contains at least 70% by weight of carbon.

2. A method of bonding together separate carbon parts with a bond of carbon which method consists in placing in contact the surfaces to be bonded, surrounding the said surfaces with an atmosphere which does not decompose to liberate carbon and which does not react with carbon at bright red heat, raising the temperature of the carbon surfaces to be bonded to bright red heat by passage of an electric current between the said surfaces and directing at the junction of the carbon parts a stream of carbonaceous liquid which is decomposable at bright red heat to deposit carbon in a hard strong condition and which contains at least 70% by weight of carbon.

3. A method of bonding together separate carbon parts with a bond of carbon which method consists in placing in contact the surfaces to be bonded, surrounding the said surfaces with an atmosphere which does not decompose to liberate carbon and which does not react with carbon at bright red heat, raising the temperature of the carbon surface to be bonded to bright red heat by passage of an electric current between the said surfaces and directing at the junction of the carbon parts a stream of carbonaceous gas which is decomposable at bright red heat to deposit carbon in a hard strong condition. and which contains at least 70% by weight of carbon.

4. A method of bonding together separate carbon parts with a bond of carbon which method consists in placing in contact the surfaces to be bonded. surrounding the said surfaces with an atmosphere which does not decompose to liberate carbon and which does not react with carbon at bright red heat, raising the temperature of the carbon surfaces to be bonded to bright red heat by passage of an electric current between the said surfaces and directing at the junction of the carbon parts a stream of carbonaceous liquid which is decomposable at bright red heat to deposit carbon in a hard strong condition and which contains at least by weight of carbon and is selected from the group consisting of hydrocarbons, heterocyclic compounds and hydrocarbon substitution products.

5. A method of bonding together separate carbon parts with a bond of carbon which method consists in placing in contact the surfaces to be bonded, surrounding the said surfaces with an atmosphere which does not decompose to libcrate carbon and which does not react with carbon at bright red heat, raising the temperature of the carbon surfaces to be bonded to bright red heat by passage of an electric current between the said surfaces and directing at the junction of the carbon parts a stream of carbonaceous fluid which is decomposable at bright red heat to deposit carbon in a hard strong condition, the said fluid containing upwards by weight of carbon.

CHARLES DESMOND GREAVES.

WILLIAM DERRICK CORLASS WALKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 363,909 Pauthonier May 31, 1887 2,188,121 Smith Jan. 23, 1940 2,272,342 Hyde Feb. 10, 1942 

